1. Technical Field
This invention relates to methods and apparatus for removing pollutants from the exhaust emissions of internal combustion engines and, more particularly, to a high efficiency catalytic converter for removing unburned pollutants from exhaust gases from an internal combustion engine or the like comprising, a catalytic chamber having an inlet connected to receive exhaust gases and an outlet therefrom, the catalytic chamber having walls of a structural fiber reinforced ceramic matrix composite (FRCMC) material comprising fibers of a generic fiber system disposed throughout a pre-ceramic resin in its ceramic state; a high temperature resistant, open celled foam disposed within the catalytic chamber within a path between the inlet and the outlet so that exhaust gases entering the inlet must pass through a cell path of the foam to exit through the outlet; and, a catalyst for unburned pollutants disposed on walls of cells of the foam.
2. Background Art
For many years, the exhaust systems of automobiles have remained substantially unchanged. There is an exhaust manifold that collects the exhaust gases emitted from the exhaust ports of the engine and outputs them into an exhaust pipe which conducts the gases to the rear of the automobile. Typically, a muffler is disposed in-line with the exhaust pipe to muffle the sounds of the gases to an acceptable level. More recently, modern exhaust systems have included a catalytic converter to complete the oxidation process of unburned particles emitted from the engine, thus reducing pollutants from the exhaust gases. In a typical prior art exhaust system of such design, the exhaust manifold is bolted or clamped to the engine and the output from the manifold is connected to an exhaust front pipe which, in turn, is connected to the catalytic converter.
As depicted in FIGS. 1 and 2, a catalytic converter 10 is nothing more than a catalyst 12 on a substrate 14. Typically, as depicted in FIG. 1, the substrates 14 are stacked in spaced parallel relationship within a metal container 16 having an inlet 18 and an outlet 20. When hot enough, the catalyst 12 causes unburned pollutants and fuel in the exhaust gases 21 passing therethrough to be further oxidized.
Thus, the efficiency of the catalytic converter 10 is directly proportional to its temperature of operation, the amount of contact area and the time of contact the exhaust gases 21 have with the catalyst 12. The above described prior art catalytic converter 10 of FIGS. 1 and 2 leaves a lot to be desired in that regard. The amount of pollutants and unburned fuel removed from the exhaust gases 21 is a function of their exposure to the catalyst 12. If there is a large area of contact, a short time is sufficient. If there is a small area of contact, a longer time of contact is required for all the pollutants and unburned fuel to contact the catalyst 12. Because of the manner of having the catalyst 12 carried by the stacked substrates 14 (or a similar arrangement) the area-to-volume ratio of the catalyst 12 is not large, the path is not conducive to maximum exposure of the exhaust gases 21 to the catalyst 12, and, additionally, the time that the exhaust gases 21 are exposed to the catalyst 12 is minimal.
Another problem with prior art catalytic converters is that because they get so hot, they must be placed outside of the engine compartment and under the vehicle. They are far from the engine itself where they could do the most good. Thus, it would be desirable to build the catalytic converter from a material that could not only withstand the required temperatures; but, in addition, be of an insulating nature so as to be able to contain the high temperatures within the catalytic converter and not pass them into the surrounding area. In that way, the catalytic converter could be moved into the engine compartment and closer to the engine without creating engine compartment temperature issues.
Wherefore, it is an object of the present invention to provide a catalytic converter which operates at a very high temperature.
It is another object of the present invention to provide a catalytic converter which is highly effective in eliminating pollutants from exhaust gases.
It is still another object of the present invention to provide a catalytic converter which provides a large area of catalyst for contact with exhaust gases in a minimum volume.
It is yet another object of the present invention to provide a catalytic converter which can be placed in the engine compartment as close to the engine as possible without creating engine compartment temperature problems.
Other objects and benefits of this invention will become apparent from the description which follows hereinafter when read in conjunction with the drawing figures which accompany it.